Internet Engineering Task Force (IETF) I. Gashinsky
Request for Comments: 6583 Yahoo!
Category: Informational J. Jaeggli
ISSN: 2070-1721 Zynga
W. Kumari
Google, Inc.
March 2012
Operational Neighbor Discovery Problems
Abstract
In IPv4, subnets are generally small, made just large enough to cover
the actual number of machines on the subnet. In contrast, the
default IPv6 subnet size is a /64, a number so large it covers
trillions of addresses, the overwhelming number of which will be
unassigned. Consequently, simplistic implementations of Neighbor
Discovery (ND) can be vulnerable to deliberate or accidental denial
of service (DoS), whereby they attempt to perform address resolution
for large numbers of unassigned addresses. Such denial-of-service
attacks can be launched intentionally (by an attacker) or result from
legitimate operational tools or accident conditions. As a result of
these vulnerabilities, new devices may not be able to "join" a
network, it may be impossible to establish new IPv6 flows, and
existing IPv6 transported flows may be interrupted.
This document describes the potential for DoS in detail and suggests
possible implementation improvements as well as operational
mitigation techniques that can, in some cases, be used to protect
against or at least alleviate the impact of such attacks.
Status of This Memo
This document is not an Internet Standards Track specification; it is
published for informational purposes.
This document is a product of the Internet Engineering Task Force
(IETF). It represents the consensus of the IETF community. It has
received public review and has been approved for publication by the
Internet Engineering Steering Group (IESG). Not all documents
approved by the IESG are a candidate for any level of Internet
Standard; see Section 2 of RFC 5741.
Information about the current status of this document, any errata,
and how to provide feedback on it may be obtained at
http://www.rfc-editor.org/info/rfc6583.
Gashinsky, et al. Informational [Page 1]RFC 6583 Operational ND Problems March 2012Copyright Notice
Copyright (c) 2012 IETF Trust and the persons identified as the
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Table of Contents
1. Introduction ....................................................3
1.1. Applicability ..............................................3
2. The Problem .....................................................3
3. Terminology .....................................................4
4. Background ......................................................5
5. Neighbor Discovery Overview .....................................6
6. Operational Mitigation Options ..................................7
6.1. Filtering of Unused Address Space ..........................7
6.2. Minimal Subnet Sizing ......................................7
6.3. Routing Mitigation .........................................8
6.4. Tuning of the NDP Queue Rate Limit .........................8
7. Recommendations for Implementors ................................8
7.1. Prioritize NDP Activities ..................................9
7.2. Queue Tuning ..............................................10
8. Security Considerations ........................................11
9. Acknowledgements ...............................................11
10. References ....................................................11
10.1. Normative References .....................................11
10.2. Informative References ...................................11
Gashinsky, et al. Informational [Page 2]RFC 6583 Operational ND Problems March 2012